Characterization of the bound residues of the fungicide cyprodinil formed in plant cell suspension cultures of wheat

The non‐extractable residues of the fungicide cyprodinil formed in heterotrophic cell suspension cultures of wheat were studied by application of [ 2‐pyrimidyl ‐ 14 C] or [ 2‐pyrimidyl ‐ 13 C]cyprodinil. The main objective was to examine whether solid‐state and liquid 13 CNMR spectroscopy can be used to examine plant bound residues of pesticides. For 14 C experiments, wheat suspensions grown on glucose as carbon source were treated with 10 mg litre −1 of 14 C‐cyprodinil. After incubation for 12 days, 20% of applied 14 C was detected as non‐extractable residues. The cell debris were treated with 0.1 M HCl (reflux), 1.0 M HCl (reflux), buffer, or 2 M NaOH (50 °C); Björkman lignin and acidolysis lignin fractions were also prepared from the debris. Radioactivity liberated and solubilized by these procedures was examined by thin‐layer chromatography and high‐performance liquid chromatography. The results showed that cyprodinil and primary metabolites contributed to the fungicide's bound residues. Most of the residues (12% of applied 14 C) remained associated with polar or polymeric/oligomeric endogenous cell materials in a stable manner. For the study with 13 C‐cyprodinil, wheat suspensions were cultivated on 13 C‐depleted glucose for four growth cycles, resulting in maximum 13 C depletion of the natural cell components to about 0.10%. During the fourth cycle, 13 C‐labelled cyprodinil was applied, and cells were incubated (12 days). Cell debris was prepared and examined by solid‐state 13 CNMR spectroscopy. Debris was then treated as described above in the 14 C experiment. Solubilized fractions were analyzed by liquid 13 CNMR spectroscopy. However, none of the 13 CNMR spectra recorded gave utilizable or unambiguous results, and all exhibited large inconsistencies, especially concerning the data from the conventional 14 C experiment. Copyright © 2003 Society of Chemical Industry